Conversion factor for CT dosimetry to assess patient dose using a 256-slice CT scanner
Conversion factor for CT dosimetry to assess patient dose using a 256-slice CT scanner
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DOI：
10.1259/bjr/66519303
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发表时间：
2006-11-01
影响因子：
2.6
通讯作者：
Endo, M.
中科院分区：
文献类型：
--
作者：
Mori, S.;Nishizawa, K.;Endo, M.
CT技术最近的快速发展已经产生了具有大量探测器行的设备，因此标准计算机断层摄影剂量指数（CTDI）不再是足够的积分范围。由于散射辐射，需要300 mm的积分范围才能在128 mm的标称射束宽度下准确测量剂量。然而，这样长的体模不便于常规用于锥束CT患者剂量检查。为了用标准剂量测定方法准确评估患者剂量，我们确定了一个转换因子（CF），该转换因子是由使用300 mm长电离室的300 mm长CTDI体模的300 mm积分范围的加权剂量分布积分（DPIw）除以使用标准CTDI体模的100 mm积分范围的加权剂量分布积分计算得出的（140 mm长），具有100 mm长的腔室。CF值随着标称束宽和有效能量的增加而增加，范围从1.5到2.0。CF值也可适用于其他CT系统，因为其剂量分布被认为类似于300 mm体模的剂量分布，并且在任何医院情况下都可用于使用标准剂量测定方法评估准确的患者剂量。
Recent rapid progress in CT technology has yielded equipment with large numbers of detector rows and standard computed tomography dose index (CTDI) is therefore no longer an adequate integration range. An integration range of 300 mm is necessary to accurately measure dose under a nominal beam width of 128 mm due to scattered radiation. However, such a long phantom is inconvenient to use routinely in cone-beam CT patient dose checking. To assess patient dose accurately with standard dosimetry methods, we determined a conversion factor (CF) which was calculated from the weighted dose profile integral (DPIw) for the 300 mm integration range with a 300 mm long CTDI phantom using a 300 mm long ionization chamber divided by that for the 100 mm integration range with a standard CTDI phantom (140 mm long) with a 100 mm long chamber. CF values increase with increasing nominal beam width and effective energy in the range from 1.5 to 2.0. CF values can also be adapted for use with other CT systems as their dose profiles are thought to be analogous to those for the 300 mm. phantom and are useful in any hospital situation to assess accurate patient doses using standard dosimetry methods.